Somehow a random internet search landed me upon the BBC Case of Charles Dexter Ward podcast. This is possibly one of the best adaptations of H.P. Lovecraft's stories I've encountered. It's like a cross between NPR's serial, the X-Files and good ol' HPL himself. BBC Radio 4 produced this 10 episode adaptation and it is completely worth binging on. I listened to the first 5 episodes on a long drive and I found it riveting.
It's a modern adaptation that uses the podcast format to good effect. It starts as a simple "locked room" mystery being investigated by two podcast journalists. They run a show called (wait for it...) Mystery Machine, replete with requests for funding. This show is so good, it actually had me reaching for my wallet. From there, it expands to a broader tale of madness, occultism, conspiracy, underground tunnels, murder and evil librarians.
I won't go into the details except to say it is completely updated to the 21st century which gives it a verisimilitude that makes it much creepier than most HPL adaptations. The production is top notch and you feel like you are listening to a smalltime investigative podcast recorded via iPhone; you're hearing their discoveries as they are happening with phone calls, audio clips, interviews etc. It's a format that invites you into the scene so that you really feel a part of it. Hopefully there will be a second season which continues the story.